package com.kingyea.mobilepolice.apimanage.accesscontrol.handle;

/**
 * @author chenjw
 * @version v1.0.0
 * @description
 * @date Created in 2018/4/7 14:29
 */

public class Base64 {


    static private final int BASELENGTH = 128;

    static private final int LOOKUPLENGTH = 64;

    static private final int TWENTYFOURBITGROUP = 24;

    static private final int EIGHTBIT = 8;

    static private final int SIXTEENBIT = 16;

    static private final int FOURBYTE = 4;

    static private final int SIGN = -128;

    static private final char PAD = '=';

    static private final boolean fDebug = false;

    static final private byte[] base64Alphabet = new byte[BASELENGTH];

    static final private char[] lookUpBase64Alphabet = new char[LOOKUPLENGTH];

    static {
        for (int i = 0; i < BASELENGTH; ++i) {
            base64Alphabet[i] = -1;
        }
        for (int i = 'Z'; i >= 'A'; i--) {
            base64Alphabet[i] = (byte) (i - 'A');
        }
        for (int i = 'z'; i >= 'a'; i--) {
            base64Alphabet[i] = (byte) ((i - 'a') + 26);
        }

        for (int i = '9'; i >= '0'; i--) {
            base64Alphabet[i] = (byte) ((i - '0') + 52);
        }

        base64Alphabet['+'] = 62;
        base64Alphabet['/'] = 63;

        for (int i = 0; i <= 25; i++) {
            lookUpBase64Alphabet[i] = (char) ('A' + i);
        }

        for (int i = 26, j = 0; i <= 51; i++, j++) {
            lookUpBase64Alphabet[i] = (char) ('a' + j);
        }

        for (int i = 52, j = 0; i <= 61; i++, j++) {
            lookUpBase64Alphabet[i] = (char) ('0' + j);
        }
        lookUpBase64Alphabet[62] = '+';
        lookUpBase64Alphabet[63] = '/';

    }

    private static boolean isWhiteSpace(final char octect) {
        return ((octect == 0x20) || (octect == 0xd) || (octect == 0xa) || (octect == 0x9));
    }

    private static boolean isPad(final char octect) {
        return (octect == PAD);
    }

    private static boolean isData(final char octect) {
        return ((octect < BASELENGTH) && (base64Alphabet[octect] != -1));
    }

    /**
     * Encodes hex octects into Base64
     *
     * @param binaryData Array containing binaryData
     * @return Encoded Base64 array
     */
    public static String encode(final byte[] binaryData) {

        if (binaryData == null) {
            return null;
        }

        final int lengthDataBits = binaryData.length * EIGHTBIT;
        if (lengthDataBits == 0) {
            return "";
        }

        final int fewerThan24bits = lengthDataBits % TWENTYFOURBITGROUP;
        final int numberTriplets = lengthDataBits / TWENTYFOURBITGROUP;
        final int numberQuartet = fewerThan24bits != 0 ? numberTriplets + 1 : numberTriplets;
        char encodedData[] = null;

        encodedData = new char[numberQuartet * 4];

        byte k = 0, l = 0, b1 = 0, b2 = 0, b3 = 0;

        int encodedIndex = 0;
        int dataIndex = 0;
        if (fDebug) {
            System.out.println("number of triplets = " + numberTriplets);
        }

        for (int i = 0; i < numberTriplets; i++) {
            b1 = binaryData[dataIndex++];
            b2 = binaryData[dataIndex++];
            b3 = binaryData[dataIndex++];

            if (fDebug) {
                System.out.println("b1= " + b1 + ", b2= " + b2 + ", b3= " + b3);
            }

            l = (byte) (b2 & 0x0f);
            k = (byte) (b1 & 0x03);

            final byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) (((b1) >> 2) ^ 0xc0);
            final byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) (((b2) >> 4) ^ 0xf0);
            final byte val3 = ((b3 & SIGN) == 0) ? (byte) (b3 >> 6) : (byte) (((b3) >> 6) ^ 0xfc);

            if (fDebug) {
                System.out.println("val2 = " + val2);
                System.out.println("k4   = " + (k << 4));
                System.out.println("vak  = " + (val2 | (k << 4)));
            }

            encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
            encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
            encodedData[encodedIndex++] = lookUpBase64Alphabet[(l << 2) | val3];
            encodedData[encodedIndex++] = lookUpBase64Alphabet[b3 & 0x3f];
        }

        // form integral number of 6-bit groups
        if (fewerThan24bits == EIGHTBIT) {
            b1 = binaryData[dataIndex];
            k = (byte) (b1 & 0x03);
            if (fDebug) {
                System.out.println("b1=" + b1);
                System.out.println("b1<<2 = " + (b1 >> 2));
            }
            final byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) (((b1) >> 2) ^ 0xc0);
            encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
            encodedData[encodedIndex++] = lookUpBase64Alphabet[k << 4];
            encodedData[encodedIndex++] = PAD;
            encodedData[encodedIndex++] = PAD;
        } else if (fewerThan24bits == SIXTEENBIT) {
            b1 = binaryData[dataIndex];
            b2 = binaryData[dataIndex + 1];
            l = (byte) (b2 & 0x0f);
            k = (byte) (b1 & 0x03);

            final byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) (((b1) >> 2) ^ 0xc0);
            final byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) (((b2) >> 4) ^ 0xf0);

            encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
            encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
            encodedData[encodedIndex++] = lookUpBase64Alphabet[l << 2];
            encodedData[encodedIndex++] = PAD;
        }

        return new String(encodedData);
    }

    /**
     * Decodes Base64 data into octects
     *
     * @param encoded string containing Base64 data
     * @return Array containind decoded data.
     */
    public static byte[] decode(final String encoded) {

        if (encoded == null) {
            return null;
        }

        final char[] base64Data = encoded.toCharArray();
        // remove white spaces
        final int len = removeWhiteSpace(base64Data);

        if ((len % FOURBYTE) != 0) {
            return null;// should be divisible by four
        }

        final int numberQuadruple = (len / FOURBYTE);

        if (numberQuadruple == 0) {
            return new byte[0];
        }

        byte decodedData[] = null;
        byte b1 = 0, b2 = 0, b3 = 0, b4 = 0;
        char d1 = 0, d2 = 0, d3 = 0, d4 = 0;

        int i = 0;
        int encodedIndex = 0;
        int dataIndex = 0;
        decodedData = new byte[(numberQuadruple) * 3];

        for (; i < (numberQuadruple - 1); i++) {

            if (!isData((d1 = base64Data[dataIndex++])) || !isData((d2 = base64Data[dataIndex++]))
                    || !isData((d3 = base64Data[dataIndex++])) || !isData((d4 = base64Data[dataIndex++]))) {
                return null;
            }// if found "no data" just return null

            b1 = base64Alphabet[d1];
            b2 = base64Alphabet[d2];
            b3 = base64Alphabet[d3];
            b4 = base64Alphabet[d4];

            decodedData[encodedIndex++] = (byte) ((b1 << 2) | (b2 >> 4));
            decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
            decodedData[encodedIndex++] = (byte) ((b3 << 6) | b4);
        }

        if (!isData((d1 = base64Data[dataIndex++])) || !isData((d2 = base64Data[dataIndex++]))) {
            return null;// if found "no data" just return null
        }

        b1 = base64Alphabet[d1];
        b2 = base64Alphabet[d2];

        d3 = base64Data[dataIndex++];
        d4 = base64Data[dataIndex++];
        if (!isData((d3)) || !isData((d4))) {// Check if they are PAD characters
            if (isPad(d3) && isPad(d4)) {
                if ((b2 & 0xf) != 0)// last 4 bits should be zero
                {
                    return null;
                }
                final byte[] tmp = new byte[(i * 3) + 1];
                System.arraycopy(decodedData, 0, tmp, 0, i * 3);
                tmp[encodedIndex] = (byte) ((b1 << 2) | (b2 >> 4));
                return tmp;
            } else if (!isPad(d3) && isPad(d4)) {
                b3 = base64Alphabet[d3];
                if ((b3 & 0x3) != 0)// last 2 bits should be zero
                {
                    return null;
                }
                final byte[] tmp = new byte[(i * 3) + 2];
                System.arraycopy(decodedData, 0, tmp, 0, i * 3);
                tmp[encodedIndex++] = (byte) ((b1 << 2) | (b2 >> 4));
                tmp[encodedIndex] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
                return tmp;
            } else {
                return null;
            }
        } else { // No PAD e.g 3cQl
            b3 = base64Alphabet[d3];
            b4 = base64Alphabet[d4];
            decodedData[encodedIndex++] = (byte) ((b1 << 2) | (b2 >> 4));
            decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
            decodedData[encodedIndex++] = (byte) ((b3 << 6) | b4);

        }

        return decodedData;
    }

    /**
     * remove WhiteSpace from MIME containing encoded Base64 data.
     *
     * @param data the byte array of base64 data (with WS)
     * @return the new length
     */
    private static int removeWhiteSpace(final char[] data) {
        if (data == null) {
            return 0;
        }

        // count characters that's not whitespace
        int newSize = 0;
        final int len = data.length;
        for (int i = 0; i < len; i++) {
            if (!isWhiteSpace(data[i])) {
                data[newSize++] = data[i];
            }
        }
        return newSize;
    }

}
